Preheat oven to 180C degrees. Cover baking sheet with foil and grease with butter to keep fish from sticking. Arrange fish on foil. Cut thin slices of butter and put 2 on each fillet. Add lemon/pepper seasoning to top of fish (if using fresh lemons, cut in half and squeeze on fish, then add pepper). Bake for approximately 15 minutes or until the fillets start to get flaky. In the meantime, bring the potatoes to boil and simmer until tender. Drain, add a knob of butter, salt and pepper and mash until smooth.

For serving, distribute mashed potato evenly between four dinner plates, top with flathead fillets and garnish with lemon wedges and fresh parsley.